Stellar Populations in Dwarf Elliptical Galaxies
In: New Light on Galaxy Evolution, p. 382-382
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In: New Light on Galaxy Evolution, p. 382-382
The new CARMENES instrument comprises two high-resolution and high-stability spectrographs that are used to search for habitable planets around M dwarfs in the visible and near-infrared regime via the Doppler technique. Aims. Characterising our target sample is important for constraining the physical properties of any planetary systems that are detected. The aim of this paper is to determine the fundamental stellar parameters of the CARMENES M-dwarf target sample from high-resolution spectra observed with CARMENES. We also include several M-dwarf spectra observed with other high-resolution spectrographs, that is CAFE, FEROS, and HRS, for completeness. Methods. We used a chi(2) method to derive the stellar parameters effective temperature T-eff, surface gravity log g, and metallicity [Fe/H] of the target stars by fitting the most recent version of the PHOENIX-ACES models to high-resolution spectroscopic data. These stellar atmosphere models incorporate a new equation of state to describe spectral features of low-temperature stellar atmospheres. Since Teff, log g, and [Fe/H] show degeneracies, the surface gravity is determined independently using stellar evolutionary models. Results. We derive the stellar parameters for a total of 300 stars. The fits achieve very good agreement between the PHOENIX models and observed spectra. We estimate that our method provides parameters with uncertainties of sigma(Teff) = 51 K, sigma(logg) = 0 : 07, and sigma[(Fe/H)] = 0.16, and show that atmosphere models for low-mass stars have significantly improved in the last years. Our work also provides an independent test of the new PHOENIX-ACES models, and a comparison for other methods using low-resolution spectra. In particular, our effective temperatures agree well with literature values, while metallicities determined with our method exhibit a larger spread when compared to literature results.© ESO 2018. ; We thank the anonymous referee for her/his comments that helped to improve the quality of this paper. VMP would like to thank Denis Shulyak for fruitful discussions. CARMENES is an instrument for the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Institut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano-Aleman), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 >Blue Planets around Red Stars>, the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucia. IR acknowledges support from the Spanish Ministry of Economy and Competitiveness (MINECO) through grant ESP2014-57495-C2-2-R. VJSB is supported by programme AYA2015-69350-C3-2-P from Spanish Ministry of Economy and Competitiveness (MINECO) Based on observations collected at the Centro Astronomico Hispano Aleman (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut fur Astronomie and the Instituto de Astrofisica de Andalucia. This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in A&AS 143, 23.
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Deriving metallicities for solar-like stars follows well-established methods, but for cooler stars such as M dwarfs, the determination is much more complicated due to forests of molecular lines that are present. Several methods have been developed in recent years to determine accurate stellar parameters for these cool stars (Teff ≲ 4000 K). However, significant differences can be found at times when comparing metallicities for the same star derived using different methods. In this work, we determine the effective temperatures, surface gravities, and metallicities of 18 well-studied M dwarfs observed with the CARMENES high-resolution spectrograph following different approaches, including synthetic spectral fitting, analysis of pseudo-equivalent widths, and machine learning. We analyzed the discrepancies in the derived stellar parameters, including metallicity, in several analysis runs. Our goal is to minimize these discrepancies and find stellar parameters that are more consistent with the literature values. We attempted to achieve this consistency by standardizing the most commonly used components, such as wavelength ranges, synthetic model spectra, continuum normalization methods, and stellar parameters. We conclude that although such modifications work quite well for hotter main-sequence stars, they do not improve the consistency in stellar parameters for M dwarfs, leading to mean deviations of around 50–200 K in temperature and 0.1–0.3 dex in metallicity. In particular, M dwarfs are much more complex and a standardization of the aforementioned components cannot be considered as a straightforward recipe for bringing consistency to the derived parameters. Further in-depth investigations of the employed methods would be necessary in order to identify and correct for the discrepancies that remain. © ESO 2022. ; CARMENES is an instrument for the Centro Astronómico Hispano-Alemán de Calar Alto (CAHA, Almería, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Científicas (CSIC), European Regional Development Fund (ERDF) through projects FICTS-2011-02, ICTS-2017-07-CAHA-4, and CAHA16-CE-3978, and the members of the CARMENES Consortium (Max-Planck-Institut für Astronomie,Instituto de Astrofísica de Andalucía, Landessternwarte Königstuhl, Institut de Ciències de l'Espai, Insitut für Astrophysik Göttingen, Universidad Complutense de Madrid, Thüringer Landessternwarte Tautenburg,Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico Hispano-Alemán), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 "Blue Planets around Red Stars", the Klaus Tschira Stiftung, the states of Baden-Württemberg and Niedersachsen, and by the Junta de Andalucía. E.D.M. and A.A.K. acknowledge the support by the Investigador FCT contract IF/00849/2015/CP1273/CT0003. We acknowledge financial support from NASA through grant NNX17AG24G, the Agencia Estatal de Investigación of the Ministerio de Ciencia through fellowship FPU15/01476, Innovación y Universidades and the ERDF through projects PID2019-109522GB-C51/2/3/4, AYA2016-79425-C3-1/2/3-P and AYA2018-84089, the Fundação para a Ciência e a Tecnologia through and ERDF through grants UID/FIS/04434/2019, UIDB/04434/2020 and UIDP/04434/2020, PTDC/FIS-AST/28953/2017, and PTDC/FIS-AST/32113/2017, and COMPETE2020 - Programa Operacional Competitividade e Internacionalização POCI-01-0145-FEDER-028953, and POCI-01-0145-FEDER-032113. This research has been funded by the Spanish State Research Agency (AEI) Project No. MDM-2017-0737 Unidad de Excelencia "María de Maeztu" – Centro de Astrobiología (CSIC/INTA). ; With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709. ; Peer reviewed
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Context. The Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs (CARMENES) survey is searching for Earth-like planets orbiting M dwarfs using the radial velocity method. Studying the stellar activity of the target stars is important to avoid false planet detections and to improve our understanding of the atmospheres of late-type stars. Aims. In this work we present measurements of activity indicators at visible and near-infrared wavelengths for 331 M dwarfs observed with CARMENES. Our aim is to identify the activity indicators that are most sensitive and easiest to measure, and the correlations among these indicators. We also wish to characterise their variability. Methods. Using a spectral subtraction technique, we measured pseudo-equivalent widths of the He I D3, Hα, He I λ10833 Å, and Pa β lines, the Na I D doublet, and the Ca II infrared triplet, which have a chromospheric component in active M dwarfs. In addition, we measured an index of the strength of two TiO and two VO bands, which are formed in the photosphere. We also searched for periodicities in these activity indicators for all sample stars using generalised Lomb-Scargle periodograms. Results. We find that the most slowly rotating stars of each spectral subtype have the strongest Hα absorption. Hα is correlated most strongly with He I D3, whereas Na I D and the Ca II infrared triplet are also correlated with Hα. He I λ10833 Å and Paβ show no clear correlations with the other indicators. The TiO bands show an activity effect that does not appear in the VO bands. We find that the relative variations of Hα and He I D3 are smaller for stars with higher activity levels, while this anti-correlation is weaker for Na I D and the Ca II infrared triplet, and is absent for He I λ10833 Å and Paβ. Periodic variation with the rotation period most commonly appears in the TiO bands, Hα, and in the Ca II infrared triplet. © ESO 2019. ; CARMENES is an instrument for the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Institut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano-Aleman), with additional contributions by the Spanish Ministry of Science, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 >Blue Planets around Red Stars>, the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucia. ; Peer Reviewed
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Ultra-hot Jupiters (UHJs) are highly irradiated giant exoplanets with extremely high day-side temperatures, which lead to thermal dissociation of most molecular species. It is expected that the neutral hydrogen atom is one of the main species in the upper atmospheres of UHJs. Neutral hydrogen has been detected in several UHJs by observing their Balmer line absorption. In this work, we report four transit observations of the UHJ WASP-33b, performed with the CARMENES and HARPS-North spectrographs, and the detection of the Hα, Hβ, and Hγ lines in the planetary transmission spectrum. The combined Hα transmission spectrum of the four transits has an absorption depth of 0.99 ± 0.05%, which corresponds to an effective radius of 1.31 ± 0.01 Rp. The strong Hα absorption indicates that the line probes the high-altitude thermosphere. We further fitted the three Balmer lines using the PAWN model, assuming that the atmosphere is hydrodynamic and in local thermodynamic equilibrium. We retrieved a thermosphere temperature 12 200-1000+1300 K and a mass-loss rate ? = 1011.8-0.5+0.6 g s-1. The retrieved high mass-loss rate is compatible with the "Balmer-driven"atmospheric escape scenario, in which the stellar Balmer continua radiation in the near-ultraviolet is substantially absorbed by excited hydrogen atoms in the planetary thermosphere. © ESO 2020. ; We thank the referee for the useful comments. F.Y. acknowledges the support of the DFG priority program SPP 1992 "Exploring the Diversity of Extrasolar Planets (RE 1664/16-1)". CARMENES is an instrument for the Centro Astronomico Hispano-Aleman (CAHA) at Calar Alto (Almeria, Spain), operated jointly by the Junta de Andalucia and the Instituto de Astrofisica de Andalucia (CSIC). CARMENES was funded by the MaxPlanck-Gesellschaft (MPG), the Consejo Superior de Investigaciones Cientificas (CSIC), the Ministerio de Economia y Competitividad (MINECO) and the European Regional Development Fund (ERDF) through projects FICTS-2011-02, ICTS-2017-07-CAHA-4, and CAHA16-CE-3978, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Institut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano-Aleman), with additional contributions by the MINECO, the Deutsche Forschungsgemeinschaft through the Major Research Instrumentation Programme and Research Unit FOR2544 "Blue Planets around Red Stars", the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucia. Based on data from the CARMENES data archive at CAB (CSIC-INTA). We acknowledge financial support from the Agencia Estatal de Investigacion of the Ministerio de Ciencia, Innovacion y Universidades and the ERDF through projects PID2019-109522GB-C51/2/3/4, PGC2018-098153-B-C33, AYA2016-79425-C3-1/2/3-P, ESP2016-80435-C2-1-R and the Centre of Excellence "Severo Ochoa" and "Maria de Maeztu" awards to the Instituto de Astrofisica de Canarias (SEV-2015-0548), Instituto de Astrofisica de Andalucia (SEV-2017-0709), and Centro de Astrobiologia (MDM-2017-0737), and the Generalitat de Catalunya/CERCA programme. A.W. acknowledges the financial support of the SNSF by grant number P400P2_186765. P.M. acknowledges support from the European Research Council under the Horizon 2020 Framework Program via ERC grant 832428. I.S. acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program under grant agreement No 694513. M.L. achkowledges the funding from the project ESP2017-87143-R. This work is based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundacion Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. ; Peer reviewed
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Due to their ubiquity and very long main-sequence lifetimes, abundance determinations in M dwarfs provide a powerful and alternative tool to GK dwarfs to study the formation and chemical enrichment history of our Galaxy. In this study, abundances of the neutron-capture elements Rb, Sr, and Zr are derived, for the first time, in a sample of nearby M dwarfs. We focus on stars in the metallicity range-0.5 ≲ [Fe/H] ≲ +0.3, an interval poorly explored for Rb abundances in previous analyses. To do this we use high-resolution, high-signal-to-noise-ratio, optical and near-infrared spectra of 57 M dwarfs observed with CARMENES. The resulting [Sr/Fe] and [Zr/Fe] ratios for most M dwarfs are almost constant at about the solar value, and are identical to those found in GK dwarfs of the same metallicity. However, for Rb we find systematic underabundances ([Rb/Fe] < 0.0) by a factor two on average. Furthermore, a tendency is found for Rb-but not for other heavy elements (Sr, Zr)-to increase with increasing metallicity such that [Rb/Fe] ≳ 0.0 is attained at metallicities higher than solar. These are surprising results, never seen for any other heavy element, and are difficult to understand within the formulation of the s-and r-processes, both contributing sources to the Galactic Rb abundance. We discuss the reliability of these findings for Rb in terms of non-LTE (local thermodynamic equilibrium) effects, stellar activity, or an anomalous Rb abundance in the Solar System, but no explanation is found. We then interpret the full observed [Rb/Fe] versus [Fe/H] trend within the framework of theoretical predictions from state-of-the-art chemical evolution models for heavy elements, but a simple interpretation is not found either. In particular, the possible secondary behaviour of the [Rb/Fe] ratio at super-solar metallicities would require a much larger production of Rb than currently predicted in AGB stars through the s-process without overproducing Sr and Zr. ; With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)
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Context. For years, the standard procedure to measure radial velocities (RVs) of spectral observations consisted in cross-correlating the spectra with a binary mask, that is, a simple stellar template that contains information on the position and strength of stellar absorption lines. The cross-correlation function (CCF) profiles also provide several indicators of stellar activity. Aims. We present a methodology to first build weighted binary masks and, second, to compute the CCF of spectral observations with these masks from which we derive radial velocities and activity indicators. These methods are implemented in a python code that is publicly available. Methods. To build the masks, we selected a large number of sharp absorption lines based on the profile of the minima present in high signal-to-noise ratio (S/N) spectrum templates built from observations of reference stars. We computed the CCFs of observed spectra and derived RVs and the following three standard activity indicators: full-width-at-half-maximum as well as contrast and bisector inverse slope. Results. We applied our methodology to CARMENES high-resolution spectra and obtain RV and activity indicator time series of more than 300 M dwarf stars observed for the main CARMENES survey. Compared with the standard CARMENES template matching pipeline, in general we obtain more precise RVs in the cases where the template used in the standard pipeline did not have enough S/N. We also show the behaviour of the three activity indicators for the active star YZ CMi and estimate the absolute RV of the M dwarfs analysed using the CCF RVs. © ESO 2020. ; CARMENES is an instrument for the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Institut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano-Aleman), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 "Blue Planets around Red Stars", the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucia. Based on data from the CARMENES data archive at CAB (INTA-CSIC).
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We announce the discovery of two planets orbiting the M dwarfs GJ 251 (0.360 ± 0.015M-) and HD 238090 (0.578 ± 0.021M-) based on CARMENES radial velocity (RV) data. In addition, we independently confirm with CARMENES data the existence of Lalande 21185 b, a planet that has recently been discovered with the SOPHIE spectrograph. All three planets belong to the class of warm or temperate super-Earths and share similar properties. The orbital periods are 14.24 d, 13.67 d, and 12.95 d and the minimum masses are 4.0 ± 0.4 M-, 6.9 ± 0.9 M-, and 2.7 ± 0.3 M- for GJ 251 b, HD 238090 b, and Lalande 21185 b, respectively. Based on the orbital and stellar properties, we estimate equilibrium temperatures of 351.0 ± 1.4 K for GJ 251 b, 469.6 ± 2.6 K for HD 238090 b, and 370.1 ± 6.8 K for Lalande 21185 b. For the latter we resolve the daily aliases that were present in the SOPHIE data and that hindered an unambiguous determination of the orbital period. We find no significant signals in any of our spectral activity indicators at the planetary periods. The RV observations were accompanied by contemporaneous photometric observations. We derive stellar rotation periods of 122.1 ± 2.2 d and 96.7 ± 3.7 d for GJ 251 and HD 238090, respectively. The RV data of all three stars exhibit significant signals at the rotational period or its first harmonic. For GJ 251 and Lalande 21185, we also find long-period signals around 600 d, and 2900 d, respectively, which we tentatively attribute to long-term magnetic cycles. We apply a Bayesian approach to carefully model the Keplerian signals simultaneously with the stellar activity using Gaussian process regression models and extensively search for additional significant planetary signals hidden behind the stellar activity. Current planet formation theories suggest that the three systems represent a common architecture, consistent with formation following the core accretion paradigm. ; With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)
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Michel Mayor (Nobel de Física 2019 por el descubrimiento del primer planeta extrasolar) ; Despite their activity, low-mass stars are of particular importance for the search of exoplanets by the means of Doppler spectroscopy, as planets with lower masses become detectable. We report on the discovery of a planetary companion around HD 180617, a bright (J = 5.58 mag), low-mass (M = 0.45M) star of spectral type M2.5 V. The star, located at a distance of 5.9 pc, is the primary of the high proper motion binary system containing vB 10, a star with one of the lowest masses known in most of the twentieth century. Our analysis is based on new radial velocity (RV) measurements made at red-optical wavelengths provided by the high-precision spectrograph CARMENES, which was designed to carry out a survey for Earth-like planets around M dwarfs. The available CARMENES data are augmented by archival Doppler measurements from HIRES and HARPS. Altogether, the RVs span more than 16 yr. The modeling of the RV variations, with a semi-amplitude of K = 2.85-0.25 +0.16 m s-1, yields a Neptune-like planet with a minimum mass of 12.2-1.4 +1.0 M on a 105.90-0.10 +0.09 d circumprimary orbit, which is partly located in the host star's habitable zone. The analysis of time series of common activity indicators does not show any dependence on the detected RV signal. The discovery of HD 180617 b not only adds information to a currently hardly filled region of the mass-period diagram of exoplanets around M dwarfs, but the investigated system becomes the third known binary consisting of M dwarfs and hosting an exoplanet in an S-type configuration. Its proximity makes it an attractive candidate for future studies. © ESO 2018. ; CARMENES is an instrument for the Centro Astronómico Hispano-Alemán de Calar Alto (CAHA, Almería, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Científicas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Königstuhl, Institut de Ciències de l'Espai, Institut für Astrophysik Göttingen, Universidad Complutense de Madrid, Thüringer Landessternwarte Tautenburg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico Hispano-Alemán), with additional contributions by the Spanish Ministry of Science through projects AYA2016-79425-C3-1/2/3-P, ESP2016-80435-C2-1-R, and AYA2015-69350-C3-2-P, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 "Blue Planets around Red Stars", the Klaus Tschira Stiftung, the states of Baden-Württemberg and Niedersachsen, and by the Junta de Andalucía. ; Peer Reviewed
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Context. The nearby ultra-compact multiplanetary system YZ Ceti consists of at least three planets, and a fourth tentative signal. The orbital period of each planet is the subject of discussion in the literature due to strong aliasing in the radial velocity data. The stellar activity of this M dwarf also hampers significantly the derivation of the planetary parameters. Aims. With an additional 229 radial velocity measurements obtained since the discovery publication, we reanalyze the YZ Ceti system and resolve the alias issues. Methods. We use model comparison in the framework of Bayesian statistics and periodogram simulations based on a method by Dawson and Fabrycky to resolve the aliases. We discuss additional signals in the RV data, and derive the planetary parameters by simultaneously modeling the stellar activity with a Gaussian process regression model. To constrain the planetary parameters further we apply a stability analysis on our ensemble of Keplerian fits. Results. We find no evidence for a fourth possible companion. We resolve the aliases: the three planets orbit the star with periods of 2.02 d, 3.06 d, and 4.66 d. We also investigate an effect of the stellar rotational signal on the derivation of the planetary parameters, in particular the eccentricity of the innermost planet. Using photometry we determine the stellar rotational period to be close to 68 d and we also detect this signal in the residuals of a three-planet fit to the RV data and the spectral activity indicators. From our stability analysis we derive a lower limit on the inclination of the system with the assumption of coplanar orbits which is i(min) = 0.9 deg. From the absence of a transit event with TESS, we derive an upper limit of the inclination of i(max) = 87.43 deg. Conclusions. YZ Ceti is a prime example of a system where strong aliasing hindered the determination of the orbital periods of exoplanets. Additionally, stellar activity influences the derivation of planetary parameters and modeling them correctly is important for the reliable estimation of the orbital parameters in this specific compact system. Stability considerations then allow additional constraints to be placed on the planetary parameters. ; German Research Foundation (DFG) FOR2544 RE 2694/4-1 German Max-Planck-Gesellschaft (MPG) Consejo Superior de Investigaciones Cientificas (CSIC) European Union through FEDER/ERF FICTS -2011 -02 Spanish Ministry of Economy German Science Foundation through the Major Research Instrumentation Programme Klaus Tschira Stiftung state of Baden-Wurttemberg state of Niedersachsen Junta de Andalucia High Performance and Cloud Computing Group at the Zentrum fur Datenverarbeitung of the University of Tubingen state of Baden-Wurttemberg through bwHPC German Research Foundation (DFG) INST 37/935 -1 FUGG European FEDER/ERF funds AYA2015-69350-C3-2-P AYA2016-79425-C3-1/2/3-P ESP2017-87676-C5-2-R ESP2017-87143-R Centre of Excellence "Severo Ochoa" award SEV-2015-0548 Centre of Excellence "Maria de Maeztu" award SEV-2015-0548 Instituto de Astrofisica de Andalucia SEV-2017-0709 Centro de Astrobiologia MDM-2017-0737 Generalitat de Catalunya/CERCA programme Science & Technology Facilities Council (STFC) ST/M001008/1 ST/P000584/1 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1161218 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) PB06 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 3180405 Hong Kong RGC grant HKU 17305618 European Research Council under the Horizon 2020 Framework Program via the ERC 83 24 28 Max-Planck-Institut fur Astronomie Instituto de Astrofisica de Andalucia Landessternwarte Konigstuhl Institut de Ciencies de l'Espai Insitut fur Astrophysik Gottingen Universidad Complutense de Madrid Thuringer Landessternwarte Tautenburg Instituto de Astrofisica de Canarias Hamburger Sternwarte Centro de Astrobiologia Centro Astronomico Hispano -Aleman Agencia Estatal de Investigacion of the Ministerio de Ciencia, Innovacion y Universidades AYA2015-69350-C3-2-P AYA2016-79425-C3-1/2/3-P ESP2017-87676-C5-2-R ESP2017-87143-R
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Table B.1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/636/A119. ; Context. The nearby ultra-compact multiplanetary system YZ Ceti consists of at least three planets, and a fourth tentative signal. The orbital period of each planet is the subject of discussion in the literature due to strong aliasing in the radial velocity data. The stellar activity of this M dwarf also hampers significantly the derivation of the planetary parameters. Aims. With an additional 229 radial velocity measurements obtained since the discovery publication, we reanalyze the YZ Ceti system and resolve the alias issues. Methods. We use model comparison in the framework of Bayesian statistics and periodogram simulations based on a method by Dawson and Fabrycky to resolve the aliases. We discuss additional signals in the RV data, and derive the planetary parameters by simultaneously modeling the stellar activity with a Gaussian process regression model. To constrain the planetary parameters further we apply a stability analysis on our ensemble of Keplerian fits. Results. We find no evidence for a fourth possible companion. We resolve the aliases: the three planets orbit the star with periods of 2.02 d, 3.06 d, and 4.66 d. We also investigate an effect of the stellar rotational signal on the derivation of the planetary parameters, in particular the eccentricity of the innermost planet. Using photometry we determine the stellar rotational period to be close to 68 d and we also detect this signal in the residuals of a three-planet fit to the RV data and the spectral activity indicators. From our stability analysis we derive a lower limit on the inclination of the system with the assumption of coplanar orbits which is imin = 0.9 deg. From the absence of a transit event with TESS, we derive an upper limit of the inclination of imax = 87.43 deg. Conclusions. YZ Ceti is a prime example of a system where strong aliasing hindered the determination of the orbital periods of exoplanets. Additionally, stellar activity influences the derivation of planetary parameters and modeling them correctly is important for the reliable estimation of the orbital parameters in this specific compact system. Stability considerations then allow additional constraints to be placed on the planetary parameters. © 2020 ESO. ; This work was supported by the DFG Research Unit FOR2544 "Blue Planets around Red Stars", project no. RE 2694/4-1. CARMENES is an instrument for the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through FEDER/ERF FICTS -2011 -02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Insitut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano -Aleman), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 "Blue Planets around Red Stars", the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucia. The authors acknowledge support by the High Performance and Cloud Computing Group at the Zentrum fur Datenverarbeitung of the University of Tubingen, the state of Baden-Wurttemberg through bwHPC and the German Research Foundation (DFG) through grant no. INST 37/935 -1 FUGG. We acknowledge financial support from the Agencia Estatal de Investigacion of the Ministerio de Ciencia, Innovacion y Universidades and the European FEDER/ERF funds through projects AYA2015-69350-C3-2-P, AYA2016-79425-C3-1/2/3-P, ESP2017-87676-C5-2-R, ESP2017-87143-R and the Centre of Excellence "Severo Ochoa" and "Maria de Maeztu" awards to the Instituto de Astrofisica de Canarias (SEV-2015-0548), Instituto de Astrofisica de Andalucia (SEV-2017-0709), and Centro de Astrobiologia (MDM-2017-0737), and the Generalitat de Catalunya/CERCA programme. This work is supported by the Science and Technology Facilities Council [ST/M001008/1 and ST/P000584/1]. J.S.J. acknowledges support by Fondecyt grant 1161218 and partial support by CATA-Basal (PB06, CONICYT). Z.M.B acknowledges funds from CONICYT-FONDECYT/Chile Postdoctorado 3180405. M.H.L. was supported in part by Hong Kong RGC grant HKU 17305618. T.H. acknowledges support from the European Research Council under the Horizon 2020 Framework Program via the ERC Advanced Grant Origins 83 24 28. Data were partly collected with the robotic 40-cm telescope ASH2 at the SPACEOBS observatory (San Pedro de Atacama, Chile) and the 90-cm telescope at Sierra Nevada Observatory (Granada, Spain) both operated by the Instituto de Astrofifica de Andalucia (IAA). This work has made use of the Exo-Striker tool (Trifonov 2019).
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Surveys have shown that super-Earth and Neptune-mass exoplanets are more frequent than gas giants around low-mass stars, as predicted by the core accretion theory of planet formation. We report the discovery of a giant planet around the very-low-mass star GJ 3512, as determined by optical and near-infrared radial-velocity observations. The planet has a minimum mass of 0.46 Jupiter masses, very high for such a small host star, and an eccentric 204-day orbit. Dynamical models show that the high eccentricity is most likely due to planet-planet interactions. We use simulations to demonstrate that the GJ 3512 planetary system challenges generally accepted formation theories, and that it puts constraints on the planet accretion and migration rates. Disk instabilities may be more efficient in forming planets than previously thought.Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science ; This research was supported by the following programs, grants, and fellowships: Spanish Ministry for Science, Innovation and Universities (MCIU) ESP2014-54062-R, ESP2014-54362P, AYA2015-69350-C3-2-P, BES-2015-074542, AYA2016-79425-C3-1/2/3-P, ESP2016-76076-R, ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, ESP2017-87143-R, ESP2017-87676-C05-02-R, ESP-2017-87676-2-2, RYC-2012-09913 (>Ramon y Cajal> program), and FPU15/01476; Israel Science Foundation grant 848/16, CONICYT-FONDECYT/Chile Postdoctorado 3180405; Deutsches Zentrum fur Luft-un Raumfahrt (DLR) 50OW0204 and 50OO1501; Italian Minister of Instruction, University and Research (MIUR), FFABR 2017; University of Rome Tor Vergata, >Mission: Sustainability 2016> fund; European Research Council under the European Union Horizon 2020 research and innovation program 694513; Mexican national council for science and technology CONACYT, CVU 448248; the >Center of Excellence Severo Ochoa> award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709); Generalitat de Catalunya/CERCA program; Fondo Europeo de Desarollo Regional (FEDER); German Science Foundation (DFG) Research Unit FOR2544 >Blue Planets around Red Stars> and Priority Programs SPP 1833, >Building a Habitable Earth> and SPP 1992, >Exploring the Diversity of Extrasolar Planets> NSF grants PHY17-48958 and PHY-1607761; Swiss National Science Foundation under grant BSGIO_155816 >PlaneltsInTime' and within the framework of the NCCR PlanetS; Queen Mary University of London Scholarship and STFC Consolidated Grant ST/P000592/1; Spanish MCIU FPI-SO predoctoral contract BES-2017-082610 and the Knut and Alice Wallenberg Foundation.
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The appendix tables are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A117 ; Context. The main goal of the CARMENES survey is to find Earth-mass planets around nearby M-dwarf stars. Seven M dwarfs included in the CARMENES sample had been observed before with HIRES and HARPS and either were reported to have one short period planetary companion (GJ 15 A, GJ 176, GJ 436, GJ 536 and GJ 1148) or are multiple planetary systems (GJ 581 and GJ 876). Aims. We aim to report new precise optical radial velocity measurements for these planet hosts and test the overall capabilities of CARMENES. Methods. We combined our CARMENES precise Doppler measurements with those available from HIRES and HARPS and derived new orbital parameters for the systems. Bona-fide single planet systems were fitted with a Keplerian model. The multiple planet systems were analyzed using a self-consistent dynamical model and their best fit orbits were tested for long-term stability. Results. We confirm or provide supportive arguments for planets around all the investigated stars except for GJ 15 A, for which we find that the post-discovery HIRES data and our CARMENES data do not show a signal at 11.4 days. Although we cannot confirm the super-Earth planet GJ 15 Ab, we show evidence for a possible long-period (P = 7030 d) Saturn-mass (msini = 51.8M) planet around GJ 15 A. In addition, based on our CARMENES and HIRES data we discover a second planet around GJ 1148, for which we estimate a period P = 532.6 days, eccentricity e = 0.342 and minimum mass msini = 68.1M. Conclusions. The CARMENES optical radial velocities have similar precision and overall scatter when compared to the Doppler measurements conducted with HARPS and HIRES. We conclude that CARMENES is an instrument that is up to the challenge of discovering rocky planets around low-mass stars.© ESO, 2018. ; CARMENES is an instrument for the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Insitut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano-Aleman), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation (DFG), the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, the DFG Research Unit FOR2544 >Blue Planets around Red Stars>, and by the Junta de Andalucia. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This work used the Systemic Console package (Meschiari et al. 2009) for cross-checking our Keplerian and Dynamical fits and the python package astroML (VanderPlas et al. 2012) for the calculation of the GLS periodogram. The IEEC-CSIC team acknowledges support by the Spanish Ministry of Economy and Competitiveness (MINECO) and the Fondo Europeo de Desarrollo Regional (FEDER) through grant ESP2016-80435-C2-1-R, as well as the support of the Generalitat de Catalunya/CERCA programme. The IAA-CSIC team acknowledges support by the Spanish Ministry of Economy and Competitiveness (MINECO) through grants AYA2014-54348-C03-01 and AYA2016-79425-C3-3-P as well as FEDER funds. The UCM team acknowledges support by the Spanish Ministry of Economy and Competitiveness (MINECO) from projects AYA2015-68012-C2-2-P and AYA2016-79425- C3-1,2,3-P and the Spanish Ministerio de Educacion, Cultura y Deporte, programa de Formacion de Profesorado Universitario, under grant FPU15/01476. T. T. and M.K. thank to Jan Rybizki for the very helpful discussion in the early phases of this work. V.J.S.B. is supported by grant AYA2015-69350-C3-2-P from the Spanish Ministry of Economy and Competiveness (MINECO). J.C.S. acknowledges funding support from Spanish public funds for research under project ESP2015-65712-C5-5-R (MINECO/FEDER), and under Research Fellowship program >Ramon y Cajal> with reference RYC2012-09913 (MINECO/FEDER). The contributions of M.A. were supported by DLR (Deutsches Zentrum fur Luft- und Raumfahrt) through the grants 50OW0204 and 50OO1501. J.L.-S. acknowledges the Office of Naval Research Global (award No. N62909-15- 1-2011) for support. C.d.B. acknowledges that this work has been supported by Mexican CONACyT research grant CB-2012-183007 and the Spanish Ministry of Economy and Competitivity through projects AYA2014-54348-C3-2-R. J.I.G.H., and R.R. acknowledge financial support from the Spanish Ministry project MINECO AYA2014-56359-P. J.I.G.H. also acknowledges financial support from the Spanish MINECO under the 2013 Ramon y Cajal program MINECO RYC-2013-14875. V. Wolthoff acknowledges funding from the DFG Research Unit FOR2544 >Blue Planets around Red Stars>, project No. RE 2694/4-1.We thank the anonymous referee for the excellent comments that helped to improve the quality of this paper.
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Context. Teegarden's Star is the brightest and one of the nearest ultra-cool dwarfs in the solar neighbourhood. For its late spectral type (M7.0 V), the star shows relatively little activity and is a prime target for near-infrared radial velocity surveys such as CARMENES. Aims. As part of the CARMENES search for exoplanets around M dwarfs, we obtained more than 200 radial-velocity measurements of Teegarden's Star and analysed them for planetary signals. Methods. We find periodic variability in the radial velocities of Teegarden's Star. We also studied photometric measurements to rule out stellar brightness variations mimicking planetary signals. Results. We find evidence for two planet candidates, each with 1.1 M minimum mass, orbiting at periods of 4.91 and 11.4 d, respectively. No evidence for planetary transits could be found in archival and follow-up photometry. Small photometric variability is suggestive of slow rotation and old age. Conclusions. The two planets are among the lowest-mass planets discovered so far, and they are the first Earth-mass planets around an ultra-cool dwarf for which the masses have been determined using radial velocities.© ESO 2019. ; M.Z. acknowledges support from the Deutsche Forschungsgemeinschaft under DFG RE 1664/12-1 and Research Unit FOR2544 >Blue Planets around Red Stars>, project no. RE 1664/14-1. CARMENES is an instrument for the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Institut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano-Aleman), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 >Blue Planets around Red Stars>, the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucia. Based on data from the CARMENES data archive at CAB (INTA-CSIC). This article is based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos Sanchez operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide. Data were partly collected with the 150-cm and 90-cm telescopes at the Sierra Nevada Observatory (SNO) operated by the Instituto de Astrofisica de Andalucia (IAA-CSIC). Data were partly obtained with the MONET/South telescope of the MOnitoring NEtwork of Telescopes, funded by the Alfried Krupp von Bohlen und Halbach Foundation, Essen, and operated by the Georg-August-Universitat Gottingen, the McDonald Observatory of the University of Texas at Austin, and the South African Astronomical Observatory. We acknowledge financial support from the Spanish Agencia Estatal de Investigacion of the Ministerio de Ciencia, Innovacion y Universidades and the European FEDER/ERF funds through projects AYA2015-69350-C3-2-P, AYA2016-79425-C3-1/2/3-P, AYA2018-84089, BES-2017-080769, BES-2017-082610, ESP2015-65712-C5-5-R, ESP2016-80435-C2-1/2-R, ESP2017-87143-R, ESP2017-87676-2-2, ESP2017-87676-C5-1/2/5-R, FPU15/01476, RYC-2012-09913, the Centre of Excellence >Severo Ochoa> and >Maria de Maeztu> awards to the Instituto de Astrofisica de Canarias (SEV-2015-0548), Instituto de Astrofisica de Andalucia (SEV-2017-0709), and Centro de Astrobiologia (MDM-2017-0737), the Generalitat de Catalunya through CERCA programme>, the Deutsches Zentrum fur Luft-und Raumfahrt through grants 50OW0204 and 50OO1501, the European Research Council through grant 6 94 513, the Italian Ministero dell'instruzione, dell'universita de della ricerca and Universita degli Studi di Roma Tor Vergata through FFABR 2017 and >Mission: Sustainability 2016>, the UK Science and Technology Facilities Council through grant ST/P000592/1, the Israel Science Foundation through grant 848/16, the Chilean CONICYT-FONDECYT through grant 31 80 405, the Mexican CONACYT through grant CVU 4 48 248, the JSPS KAKENHI through grants JP18H01265 and 18H05439, and the JST PRESTO through grant JPMJPR1775. ; Peer Reviewed
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The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M dwarf. These spectra cover the wavelength range 520¿1710 nm at a resolution of at least R >80 000, and we measure its RV, H¿ emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q, and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700¿900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m s¿1 in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3-4 m s-1. © ESO 2018. ; We thank an anonymous referee for prompt attention and helpful comments that helped to improve the quality of this paper. CARMENES is an instrument for the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Insitut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano-Aleman), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 >Blue Planets around Red Stars>, the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucia. This work has made use of the VALD database, operated at Uppsala University, the Institute of Astronomy RAS in Moscow, and the University of Vienna. We acknowledge the following funding programs: European Research Council (ERC-279347), Deutsche Forschungsgemeinschaft (RE 1664/12-1, RE 2694/4-1), Bundesministerium fur Bildung und Forschung (BMBF-05A14MG3, BMBF-05A17MG3), Spanish Ministry of Economy and Competitiveness (MINECO, grants AYA2015-68012-C2-2-P, AYA2016-79425-C3-1,2,3-P, AYA2015-69350-C3-2-P, AYA2014-54348-C03-01, AYA2014-56359-P, AYA2014-54348-C3-2R, AYA2016-79425-C3-3-P and 2013 Ramon y Cajal program RYC-2013-14875), Fondo Europeo de Desarrollo Regional (FEDER, grant ESP2016-80435-C2-1-R, ESP2015-65712-C5-5-R), Generalitat de Catalunya/CERCA programme, Spanish Ministerio de Educacion, Cultura y Deporte, programa de Formacion de Profesorado Universitario (grant FPU15/01476), Deutsches Zentrum fur Luft- und Raumfahrt (grants 50OW0204 and 50OO1501), Office of Naval Research Global (award no. N62909-15-1-2011), Mexican CONACyT grant CB-2012-183007.
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